1. Technical Field of the Invention
The present invention relates generally to supplying power to a user from a remote position and more particularly to a method of remotely powering a device such as a lunar rover.
2. Discussion of the Related Art
Interest in building a permanent lunar base has substantially increased. Such a base would be a test bed for future Mars missions and would also be used for extensive science and exploration missions on the lunar surface. The lunar base would be a fixed, permanent structure with much surrounding infrastructure. However, this cannot satisfy the needs of geologists and other planetary scientists who would like to visit many distant lunar locations with minimum infrastructure and maximum mobility. Assaying lunar resources for potential commercialization would also require high mobility. Such needs have made the concept of the long-distance lunar rover attractive. The rover would be required to support four crew members for several weeks to months, have good mobility for long-distance missions, and provide adequate power for performing detailed science analysis and crew support. The potential advantages of such a rover, from a geologist's point of view, are detailed in a proposed lunar science mission by Cintala, Spudis, and Hawke in "Advanced Geologic Exploration Supported by a Lunar Base: A Traverse Across the Imbrium-Proellarum Region of the Moon", found in Lunar Bases and Space Activities of the 21st Century, W. Mendell, Ed., Lunar and Planetary Institute Press, pp. 223-37, 1985. This proposed lunar expedition would traverse the Imbrium Basin and its environs for a total route distance of almost 4,000 km, visiting 29 separate localities in an attempt to characterize the process involved in the formation and evolution of the lunar surface. This trip equals approximately 37 percent of the Moon's circumference of 10,933 km. No details concerning the rover to accomplish this mission or its power source were given in the proposal.
Previous rover studies have focused on advanced rovers powered by nuclear reactors and fuel cells. The most detailed study to date was done by Eagle Engineering, Inc. and is contained in NASA Contractor Report No. 172,077, July, 1988, entitled "Lunar Surface Transportation System Conceptual Design, Lunar Base Systems Study Task 5.2". There, the long-duration rover was made up of eight vehicles linked together having a total mass of 17,560 kg. The train configuration consisted of a primary control vehicle, a habitation trailer unit, five auxiliary power carts providing 25 kW and 7000 kW-h of energy to the train, and finally an experiment and sample trailer. Power was supplied by fuel cells which made up one-third (5900 kg) of the total system mass. In addition, this rover could accomplish a 3000-km round trip, 42-day mission with a crew of four at a maximum speed of 15 km/hr. No provision was made in this study for the mass of equipment needed to generate the H.sub.2 and O.sub.2 reactants for the fuel cells. This additional mass component could significantly increase the "total" system mass.
Rovers powered by nuclear reactors capable of providing 25 kW of electric power have large masses due to the required nuclear shielding of the reactor. Also, since the total reactor usually is not shielded, the unshielded area behind the reactor is not accessible to rover personnel. Rovers powered by solar photovoltaics at 25 kW of electricity would require 81 m.sup.2 of solar array. Such an array would be much larger than the rover and have high mass. This rover would not be able to operate at lunar night unless there was a large storage capability on board.
Laser-power-beaming studies have shown that significant payoff can be achieved by decoupling the prime power source from the user. More flexible power infrastructures are achieved for a variety of space missions, including powering of low power robotic rovers to high power laser propulsion.